Ardelyx Inc. could have a rocky row to hoe when it makes its case for tenapanor, as a hyperphosphatemia therapy in adults with chronic kidney disease, before the U.S. FDA’s Cardiovascular and Renal Drugs Advisory Committee Nov. 16. The big question facing the adcom is whether the change in baseline serum phosphorous levels achieved by the drug is clinically meaningful. Clearly, FDA reviewers don’t think so, as that question already has resulted in delayed PDUFA dates, a complete response letter and two formal dispute resolution requests.